How To Identify, Prevent And Treat Powdery Mildew On Plants

That white fuzzy mold that is spreading on the leaves of your houseplants or garden plants is powdery mildew. It is caused by the spores of group of small fungi of the Erysiphales order. Many species in this order can appear as white or off white dust or powder that spreads on leaves and stems.

Powdery mildew spreads fast on plants; it is a fungal infection that appears as white patches of powder on the leaves and stems of plants. It is a problem but in most cases it does not compromise the life of adult plants. It is also fairly easy to cure with simple home-made remedies like neem oil, soap and baking powder.

Get ready for a detailed, step by step and comprehensive guide on powdery mildew: we will learn to recognize, it, treat it, get rid of it and, above all, avoid it!

What Is Powdery Mildew?

What Is Powdery Mildew?

Powdery mildew is a patina of white dust caused by fungi of the Erysiphales order, a group of sac shaped fungi which reproduce with both sexual spores (ascospores) and asexual spores (conidia). The containers of these asexual spores, called conidhores, are the actual white dust you see on the leaves.

There are many species of fungi within this order that cause powdery mildew, and the most commons are Podosphaera xanthii and Erysiphe cichoracearum.

So, powdery mildew itself is not the fungus, but a consequence of the life cycle of the fungus.

How to Identify Powdery Mildew On Plants

How to Identify Powdery Mildew

Powdery mildew is a very easy plant complaint to identify or diagnose. You will recognize it because of its appearance but also its behavior, in particular, how it spreads. There will be different stages of the infestation. So, the symptoms you will see now will increase in gravity (size) and number as the fungus spreads.

Here’s how to identify powdery mildew damage on plants:

  • A few small white dots may start appearing on the leaves. The first symptoms are small and difficult to get.
  • These dots tend to start on the lower leaves of your plants. This is possibly because they receive less light. However, this is not a rule.
  • The white dots will spread steadily like stains.
  • You will notice that these stains look more and more like flour, or dandruff… Basically a white powder.
  • In later stages, the leaves may twist or change shape.
  • The affected leaves may turn yellow.
  • Overall, the plants will look sickly and unhealthy.
  • In advanced stages, you will see leaf dropping.
  • In advanced stages  powdery mildew will stunt the growth of your plants.
  • In advanced stages, powdery mildew will reduce blooming and fruiting.

Try to catch powdery mildew at the early stages to reduce damage and make treatment easy.

How to Powdery Mildew Appears on Your Plants

How to Powdery Mildew Appears on Your Plants

Powdery mildew starts as small white dots on any part of the plant above ground. Most commonly, these are leaves, but not necessarily.

As the fungi reproduce, these white dots spread into patches. These patches, if you look at them closely, will look like fairly densely scattered dust that attaches to the leaves, stems or more rarely other parts of your plant.

You can easily remove this dust by rubbing the leaf or affected area. This, however, is good to diagnose the disease, but it is not a valid treatment. You risk spreading the spores.

So do it gently once on a small area if you need to be sure you are dealing with powdery mildew. After that, pass to the treatment.

Is Powdery Mildew Dangerous for Plants?

Is Powdery Mildew Dangerous for Plants?

Powdery mildew is a problem for plants but it is not seriously dangerous in many cases. The most common damages powdery mildew will cause are:

  • An unpleasant look. The white powder is not pleasing aesthetically and it makes your plant look ill.
  • A weakening of the plant and its immune system. Loss of leaves may occur.
  • In crops, a serious infestation of powdery mildew can cause significant yield reduction.
  • Because the plant is weakened, it can be attacked by other parasites or diseases later on.

Is Powdery Mildew Lethal to Plants?

Is Powdery Mildew Lethal to Plants?

Powdery mildew is not usually lethal to healthy plants. If plants die because of powdery mildew usually:

  • They had prior conditions.
  • They are very young.

However, the diseases that may follow powdery mildew may spell the death of your plant.

How Powdery Mildew Spreads

How Powdery Mildew Spreads

Powdery mildew spreads from plant to plant in different ways.

  • The most common way is by sticking its spores to small insects, especially aphids and woolly aphids.
  • It can also be airborne, which means that it comes to your plants via the air (wind or breeze or any air movement).

Look Out For Aphids And Powdery Mildew

Look Out for Aphids and Powdery Mildew

Aphids can carry powdery mildew, therefore, especially woolly aphids. So, these tiny insects can be an indicator of a possible future powdery mildew infestation.

If you have an aphid problem, keep alert because even after they have gone, the spores  may open and infest your plants with powdery mildew.

Most Affected Parts of Plants by Powdery Mildew

Most Affected Parts of Plants by Powdery Mildew

Leaves are by far the parts of plants that powdery mildew affects most. Also check on the back of leaves, which are very easily infested by powdery mildew.

But there are other parts, like stems, especially green and young ones, that can be affected quite frequently. The whole aerial part of the plant can be affected, to be correct, but other parts are not as common as these.

When the infestation starts, usually it is the lower leaves that are affected.

Plants Most Hit by Powdery Mildew

Plants Most Hit by Powdery Mildew

Not all plants are as likely to get powdery mildew. Some are more “attractive” to this mold than others. Plants that are more at risk have common features:

  • Soft foliage.
  • Soft petioles and stems.
  • They are shade loving plants (or plants that do not grow in full Sun).

Houseplants are very susceptible to powdery mildew. Some mor than others though, for example:

  • Begonias
  • African violets
  • Philodendron
  • Monstera
  • Jade plant
  • Cannabis

Outdoor plants, however, are not at all immune from powdery mildew. In fact, some are quote at risk, like:

  • Cucurbits (squash, cucumbers, melons, pumpkins)
  • Legumes (peas, beans etc.)
  • Roses
  • Nightshades (tomatoes, peppers and eggplant)
  • Oak trees

Conditions for Powdery Mildew

Conditions for Powdery Mildew

The main reason why your plants get powdery mildew is climatic. If the weather is warm and humid, it will provide the ideal conditions for powdery mildew.

This may happen because the summer is particularly wet (it does happen!) Alternatively, you may be living in a generally humid climate. In this case, powdery mildew may become a constant hassle. Or it may be that the position of your land (in a dip in the land, with little exposure to sunlight etc…) may create this microclimate.

Another cause is monoculture. Diseases always spread fast from plant to plant of the same type.

Indoors, the main problem is air humidity. Indoors, it can rise very fast. Ventilation and humidity control are therefore key to avoiding it.

How to Get Rid of Powdery Mildew on Plants

How to Get Rid of Powdery Mildew on Plants

Treating and eliminating powdery mildew is quite simple and cheap. In the past, people turned to chemical products to do this.

However, they are bad for the environment. Bad for your plants, bad for your family, bad for your food and expensive. And totally unnecessary.

We will see easy, effective and cheap home-made remedies for powdery mildew that will not fail you.

1: Neem Oil For Powdery Mildew

Neem Oil for Powdery Mildew

Neem oil is excellent against powdery mildew. This oil is becoming the “must have” bottle in every organic gardener’s cupboard. In fact, it is perfectly innocuous to plants and to the soil. But it is it is a very powerful fungicide.

It also kills pests, it has actually so many different uses for a gardener that it replaces, in one, cheap, long lasting and safe bottle most chemical products you can buy on the market.

And for powdery mildew, you will only need a tiny bit. How, her we go!

  • Take a 1 liter (1/4 gallon) spray bottle.
  • Melt a nugget of Castile or any natural soap in some warm water.
  • Pour it into the spray bottle.
  • Fill the bottle with with water.
  • Add one tablespoon of pure organic neem oil.
  • Shake well.
  • Spray your plants abundantly.

You may have to repeat it after 10 to 15 days.

Alternatively, there’s a more laborious, but at the same time simpler method.

  • Pour two tablespoons of neem oil in a cup.
  • Take a soft cloth.
  • Dip it in the neem oil.
  • Dab all the plant carefully, paying attention to cover the undersides of leaves.

This is simple if you have one plant. It is not ideal if you need to treat a field, flower bed etc. But for the individual houseplant it is the ideal method.

2: Apple Cider Vinegar For Powder Mildew

Apple Cider Vinegar for Powder Mildew

Apple coder vinegar is another natural remedy which is becoming very popular and you can use it for powder mildew.

In fact, it too is a strong fungicide, and as you can use it for nail fungus, so you can use it with this tiny but messy plant fungus.

  • Get a 1 liter (1/4 gallon) spray bottle.
  • Pour about one tablespoon of apple cider vinegar in it.
  • Fill the spray bottle with water.
  • Shake well.
  • Spray your plants profusely.
  • Make sure you get the underside of leaves.

You may have to repeat the operation after one or two weeks.

Don’t worry about the apple cider vinegar going into the soil; it will actually stimulate root growth and strengthen your plants.

Only make sure you use it in low concentration, like we have shown you. Otherwise, it may change the acidity of the soil, and that ca be a problem.

3: Baking Soda Spray To Control Powdery Mildew

Baking Soda for Powder Mildew

Baking soda is one of the oldest home remedies for powder mildew and other fungi. It may not be as strong as neem oil, but if your plant is not heavily affected, it may just be enough.

Using baking soda, however, is very good prevention against powder mildew.

The only drawback of this method is that the sodium on the baking soda may end up in the soil. To avoid problems, avoid using it far too many times or to use high concentrations. Also the better drained and loose your soil is, the easier it will be to “wash the sodium out”.

Here is how to use baking soda to prevent powdery mildew on plants:

  • Get a 1 liter spray bottle (1/4 gallon).
  • Put half a tablespoon of baking soda in it.
  • In a bowl, put 1 liter of lukewarm water.
  • Grate a nugget of natural soap in it.
  • Stir till the soap has dissolved.
  • Pour into the bottle.
  • Shake well.
  • Now spray your plants covering all of their aerial part of the plants.

This treatment too may need repeating after about 10 to 14 days.

4: Milk Spray For Powder Mildew

The lactic acid in milk is a natural fungicide which you can use to get rid of powder mildew.

This remedy too is not very strong, but it can be good if you don’t have other treatments or ingredients and it may be enough if the infestation is young or small. Here is how you can do it:

  • Get a 1 liter (1/4 gallon) spray bottle.
  • Fill it with 9 parts water and 1 part milk.
  • Shale well.
  • Spray on the affected parts of your plants.
  • Place the plants in the Sun to dry up.

You will have to repeat this weekly to keep the plants free from powder mildew.

How to Prevent Powder Mildew

How to Prevent Powder Mildew

It is time to think about preventing powder mildew, now that we have seen four different natural and home-made remedies to treat plants affected by it. Prevention is always better, for human, animal, and plant ailments.

Sometimes it will be easy to prevent powder mildew, and sometimes it may just happen despite all your efforts.

Do not beat yourself up if it happens. Spores are small, even invisible… Plus, the sudden wet week in summer does happen. And it is more than enough to cause powder mildew.

Having said this, what can you do to prevent powder mildew?

  • Ventilate your plants. This is by far the best prevention method. Change the air in rooms, green houses etc. Outdoors, don’t block off plants in potentially humid places with hedges etc.
  • Keep checking your plants. Act at the very first sign of powder mildew. This will make treating easier.
  • Mind aphids, especially woolly aphids. As you know, these can carry the spores.
  • Beware of warm temperatures. Powder mold’s favorite temperature is between 60 and 80oF (15 and 80oF). Instead, when the temperature drops under 50 or goes above 90oF (10 and 32oC respectively) powder mold struggles and colonies are reduced significantly.
  • Make sure your plants get enough sunlight. Underexposure can be a cause of powder mildew. It is related to the humidity a pant gets. If a plant needs warm, bright and sunny conditions, it means that it will need less air humidity than it finds in shadier paces.
  • Use preventative sprays (like baking soda, or milk). This, especially if the conditions are getting ideal for powder mold. Foe example if the weather gets humid, if you see aphids, if winds are low…
  • Water carefully. Overwatering can cause humidity and in turn this can attract our dusty fungal guests.

No More Powder Mildew

No More Powder Mildew

Now you know everything about this unwelcome and dusty guest to your plants. You know what it is, what it looks like and why it comes.

You also know how it spreads, what damage it can cause to your plants and which plants it most likely affects.

But above all, now you know simple, cheap and safe ways of treating it if it comes, and you also have clear tips on how to prevent powder mildew from ever coming to your houseplants, vegetable or garden flowers.

Updated on by Amber Noyes

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